GENERATORS?UPS?INVERTERS?

[murdock]

Checking if a inverter/UPS if not specified in the specification sheet can only really been done by means of a Oscilloscope, most electronic guys have such equipment, TV repair shops Radio repair shops and so on. Funny enough is that Sine wave inverter manufacturers are proud of their products and thus have no problem on adding Sine wave inverter on the description. If not mentioned directly on the Info pages or specification, be careful, that probably the real reason why not mentioning it and selling it cheap, lol Keep on buying until you learn to do the right thing and read the info! Most reliable inverters have a pre-power stage we call a Power Factor correcting circuit which serve a double purpose inside the inverter, firstly to make sure it can run at a good Power Factor of at least 0.9 that makes the system very efficient and secondly it compensate for input power fluxuations, thus it will easily work also from a generator. Good recommended quality worldwide systems are the Cotek systems (only inverters not Ups all sine wave) very expensive and the "POWERVERT" systems (UPS and inverters all sine wave) very good and relative cheap but only available from June onwards in SA.

if the person selling the equipment cant provide the equipment to test...best you find someone who can...how do they verify the equipment they are selling is correct and functioning correctly during commisioning.

Now is a good time to enquire about generators and invertors cause most of the fly by nights are out of bussiness or found other opitunities to make quick money.

[Daves]

Hi all, is this forum still active?

daves

[Bransby]

how will I be able to check or should I call an electrician in?

[deon43]

Hey Guys and Girls, please post your enquiry on what you need and what application you want to drive e.g. the load or devices and for how long you want to sustain the power backup, Inverters are obvious the correct way to go as they are silent, noiseless, smokeless and on and on and very reliable. We are professional engineers on this applications and we do units from 600 watt up to 285 KW with online or offline technology. note the two differences, a inverter and a ups are quite different as UPS units, unless specified otherwise are shorterm backups and mostly “Kwasi� wave or as the public calls it Square wave (A step related formed sine wave, looks like staircase and bad for inductive equipment) and really very inefficient and bad for any system. We believe in making use only of Sine wave inverter equipment and with the high production volumes it does cost more or less the same these days as the Cheaper Square wave crap of earlier. Good advice, do it correct the first time and get a reliable supplier!! You can mail me on deon@electro-web.co.za and we will gladly help.

[Dave A]

how will I be able to check or should I call an electrician in?

An electrician might help, although not many have the sort of equipment needed to analyse the wave shape. You could test to see if the UPS will accept the power from the inverter. In fact, when setting up any backup power situation it's a good idea to proactively test it and not just wait for a crisis to occur.

Ultimately you probably need to be looking at your overall backup power strategy. Why do you need a UPS running off an inverter supply in the first place?

[Dave A]

With Eskom saying it's going to take 5 years to get more generation capacity online and existing reserve generation capacity tight, I don't think the crisis is over

[ians]

With Eskom saying it's going to take 5 years to get more generation capacity online and existing reserve generation capacity tight, I don't think the crisis is over

@Dave ...you mentioned 5 years .... eeeeeish

[Dave A]

@Dave ...you mentioned 5 years .... eeeeeish

I see that was in 2009

We were so young and naïve back then

[SeanM]

Evening All

I recently install a 5kva hybrid inverter upon doing my test I noticed that when the installation was being fed from the grid all my sockets tested as they should and the earth leakage tripped at 20 ma. When I changed over to the inverter my polarity tester indicated that the earth was now missing from the socket circuits.

I then proceeded to test on the input to the inverter:

L-N = 235 volts
N-E = 0 volts

On the output of the inverter:
L-N= 230 volts
N-E = 90 volts

I then switched the inverter off and had the grid power still feeding the inverter

Input:

L-N = 235 volts
N-E = 0 volts

Output:

L-N = 0 volts
N-E = 24 volts

It seems that the inverter is faulty.

[GCE]

Hi SeanM

It appears that your inverter output is not isolated from the input .

You need to earth the neutral on the output when it loses the grid and remove the earth under grid operation.In the higher quality units , the output is isolated from the input whether it is in grid or back up mode.

Make sure that the output is not earthed when on grid mode as you could become the star earth point for the transformer feeding the street under a fault condition , or if somebody steals the earth neutral link in the sub station.
It is why you have to install 4 pole change over switches on back up equipment and the reason for 6.1.6.

Basically only the supplier can earth the neutral - When you use municipal supply , they are obviously the supplier - when you are in back up mode , you are the supplier.

6.1.6 The neutral conductor shall not be connected direct to earth or to the
earth continuity conductor on the load side of the point of control except as
allowed in 7.16.4